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4WD Axle Actuator Housing

What is a 4WD axle actuator housing and where is it located?

The four-wheel drive axle actuator housing, sometimes called the axle disconnect housing, is part of the differential that houses the gears and shift fork required to lock both front axles together. Four-wheel drive (4WD) systems allow the engine to drive all four wheels of a vehicle simultaneously. The benefit of a four-wheel drive system is that, by being able to drive four wheels instead of two, you have the ability to double the amount of force needed for your tires to apply themselves to the surface they're moving on. So, both traction and acceleration are enhanced. This is particularly useful in low-traction conditions where wheel slippage (when the force applied to a tire is greater than the amount of force that the tire can apply against the ground or the ground can apply against the tire) is much more likely to occur, such as off-roading, wet or snowy conditions, climbing slippery hills, or on dirt roads. For these reasons a 4WD system is common on trucks and SUVs—including Jeep models.

The axle actuator works together with the transfer case to send torque to all four wheels. The transfer case connects the input from the transmission to the rear and front driveshafts. Most of the time, the vehicle is in rear-wheel drive (RWD). When 4WD is engaged, the transfer case engages the front driveshaft. It’s still necessary, though, to connect the two front constant velocity (CV) axle shafts. This is done via a front differential and the axle actuator.

The axle actuator housing is found on the differential. When 4WD drive is engaged, a shift fork inside the axle actuator housing slides a locking collar over two gears locking both driver and passenger side axles together. In some 4x4 vehicles, those with automatic 4WD, this process occurs automatically. In others, with selective 4WD, the driver can choose to engage 4WD or RWD with a switch. These have slightly different axle actuator housings and have actuator solenoids mounted to them.

The axle actuator housing contains and protects the shift fork, locking collar, and gears. Those moving parts need to be protected from the elements and kept properly lubricated.

How do I know if my 4WD axle actuator housing needs to be replaced?

Due to its location underneath the vehicle, the axle actuator housing can be exposed to dirt, road salt, and other pieces of road debris. These can damage the actuator housing, which will make it less effective at protecting the moving parts inside. Then, dirt can get inside of the actuator to cause bearing wear or lubricant leakage. Wear can also simply occur over time from use. If you try to shift the vehicle into 4WD at speed, the high forces involved might crack the actuator housing. This is another good way to let dirt into or lubricant out of the axle actuator.

If your axle actuator isn’t working, you won’t be able to lock the front axles together causing a very ineffective 4WD system and causing power to be transmitted to only two or possibly three wheels.

Can I replace a 4WD axle actuator housing myself?

Axle actuator housings from 1A Auto are complete assemblies, containing the gears and shift fork. That puts replacing a 4WD axle actuator, luckily, within the reach of a do-it-yourselfer. You can replace the whole actuator housing without worrying about reconstructing the parts inside (which were likely damaged anyway). You may have to disconnect some suspension parts in order to make more working space for yourself. Then, you will need to disconnect the CV axle from the actuator. If you have selective 4WD, you will also have to remove the actuator solenoid. Since the solenoid sees the same amount of use as the actuator housing, you might want to replace the solenoid at the same time as the actuator housing. The actuator can be removed by simply unbolting it from the differential. With that done, you can install the new part by reversing the previous steps.

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